Lizards Need Social Lives, Too

Social isolation, especially early in life, can be disastrous for birds and mammals. It can result in adults with increased anxiety and stress, worse performance on cognitive tests, and abnormal social behavior. Early social isolation can even have deleterious physiological effects, including a decreased lifespan.

But what about lizards? They were long-assumed to be asocial and behaviorally ‘simple.’ But more recent research has shown some lizards are devoted parents and mates that can distinguish their kin from strangers and recognize individuals. Many lizards spend the first few months of their lives in the company of their siblings or a family group, where they might learn important life lessons and skills.

To investigate the effects of early social isolation on lizards, Cissy Ballen, Richard Shine, and Mats Olsson of the University of Sydney hatched veiled chameleons in the lab and reared them either in isolation or in groups of four animals.

Not much research has been done on the social lives of wild chameleons, but hatchlings that are born around the same time are known to be briefly aggregate. It’s possible that social experiences during this period may be important for their development.

Ballen and her colleagues staged interactions between pairs of chameleons when the animals were two months old. The researchers found the two groups didn’t differ in aggression, but chameleons raised in isolation were more submissive than their siblings raised in groups. The isolation-reared chameleons tended to flee or curl into a ball during confrontations with other chameleons, and they adopted darker and less green colors than the group-reared chameleons. The researchers also tested the foraging ability of the animals, and found that group-reared chameleons seized their prey (crickets) faster than isolation-reared chameleons.

These chameleons are likely not unique among reptiles in their sensitivity to social conditions. In fact, chameleons have relatively simple social lives compared to reptiles like skinks, some of which give birth to live young and live in groups of close relatives. Young skinks grow up among parents, older siblings, and their litter mates. Early social isolation for these reptiles might severely impair their future social interactions.

Social isolation might also be deleterious for reptiles that use complex signals in social interactions. Many reptiles have elaborate visual or vibrational displays that they use in contests over mates and territories. A large body of research has demonstrated that songbirds raised in isolation are unable to produce or process the complex songs necessary for social success in their species. It’s currently unknown how early social experiences affect a lizard’s success in contests as an adult, or if isolation has the same socially crippling effect it has in songbirds.

These results also have implications for the fate of reptiles in captivity, which are often raised in social isolation under the assumption that social experience is not relevant for their development. If a ‘putatively asocial’ lizard (as the authors call the veiled chameleon) is affected by early social isolation, then this assumption may not hold for any reptile species. It seems that reptiles, like mammals and birds, can benefit from an early environment rich in social interaction.